article 2013 Participation and performance trends in ultra-endurance running races under extreme conditions -‘Spartathlon’versus‘Badwater’ Kristina da Fonseca-Engelhardt, Beat Knechtle, Christoph Alexander Rüst, Patrizia Knechtle, Romuald Lepers, Thomas Rosemann JournalExtreme Physiology & MedicinePopulationultramarathoners